[postgis-devel] Astronomical extensions
Markus Schaber
schabi at logix-tt.com
Thu Nov 2 05:35:45 PST 2006
Hi, Jim,
Jim Bosch wrote:
> - Astronomers deal with ellipses, and often care very much about
> ellipse-specific things. While approximating ellipses as polygons is
> perfectly fine for topological operations (so there's no need to worry
> about multi-ellipses, etc.), being able to extract things like
> ellipticity and orientation angle from individual ellipses is of utmost
> importance. So I'd need to make an ellipse data type, and add the
> necessary operators for it to interact sensibly with existing PostGIS
> types. I'm not sure, however, whether I should make this a new subtype
> of the PostGIS Geometry type, or a new PostgreSQL type altogether.
> There are probably a host of other more subtle questions as well.
In case you're going to extend the PostGIS types, please see whether
there are any OpenGIS standards one can implement or ignore :-)
> - Astronomers use a totally different set of coordinate systems. A
> very basic gnomonic projection is by far the most common, but it is
> described very differently (not to mention the fact that everything is
> inside-out, since we look at the sky, not the ground). The astronomical
> community already has a large set of standard coordinate systems and
> standard representations for them, as well as several libraries (similar
> to PROJ4 in nature) to do the actual transformations. This step, then,
> at least seems straightforward: add one of these libraries as an
> alternate backend for transforms, and find a way to put the astronomical
> coordinate systems in the spatial reference table.
What about adding the transformations to proj4?
HTH,
Markus
--
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf. | Software Development GIS
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